Locking screw-thread



.UNITED STATES IRVING C. WOODWARD, OF CHICAGO, ILLINOIS, ASSIGNOR TO EUGENE OE CHICAGO, ILLINOIS.

PATENT OFFICE.

A. WOODWARD,

LOCKING SCBEVf-THREAD.

Specification of'Letters Patent.

Patented Feb. 22, 1921.

- Application filed February 3, 192i). Serial No. 356,018.

To all whom it may concer/a:

Be it'known that I, InviNe C. VOODWeRD, a citizen of the United States of'America,

and a resident of Chicago, county of Cook,

and State of Illinois, have invented certain new and useful Improvements in Locking Screw-Threads, of which the following is, a spe'cication.

The main objects of this invention are to provide'an improved form of screw thread which, after it has been formed with a uniform pitch, may more easily than a standard thread have the Vdistance from the center of one thread to the center of the next thread increased or decreased either through the threaded'members entire length or part of it, and which will frictionally loch together two vcoactirng threaded members when at least one of them has this improved thread and when one of them has either a uniformly greater or less pitch than the other through itsentire threaded length or has a greater or less difference in the distance of the center of one thread to the center of the next thread through only a part of its threaded length.

A specific embodiment ef this invention is shown in the accompanying drawings in which- 1Figure lis a longitudinal section of a nut provided Lwith the improved screw-thread designed for use with a bolt having the usual U. S. Form thread.

' Fig. 2 is a similar section showing the nut in position on the bolt and indicating in an exaggerated way the expansion of the thread lielixof the nut which causes it to lockingly grip the threads of the bolt.

Ilig. 3 is a sectional view showing the iin proved screw-threaded applied to a stud bolt designed to coperate with a tapped hole having U. S. Form screw-threads.

Fig. t is-an enlarged sectional detail of the screw thread illustrating the invention as applied t0 the usual U. Form thread.

In the form shown in the drawing, both of the interitting threads are of standard shape with the exception that the thread grooves of one of the members (in Fig. 2, the nut, and in Fig. 3, the bolt) are deepened to permit of a slight axial yielding of its thread helix when the male and female members, which are made with a different uniform pitch of threads are forcibly made to coact. Both In Fig. 4 of the drawing, the special thread i with deepened thread grooves is shown in cross-section and the form of a co-acting U. S. F. thread is indicated in dotted outline with its apex at 2. The pitch line (or cylinder) of both the standard and special threads is indicated by broken line A-'-A, this being exactly half way between the root and crestrlines of the standard thread but closer t0 the crest than to the root or the special thread.

If both members were threaded Vwith U. S. Form threads, the distance between the apex 2 or" one thread and thebottom of the groove of the other thread would be considerably less than that indicated, namely, merely enough for clearance.

The special thread, as shown, has a greater Vdepth than a standard Qthread so that the distance between the center of one thread to the center of any other thread may be more easily changed.

In some cases when the special thread coacts with a U. S. Form thread, suicient depth of thread at the bottom may be obtained by continuing to a sharp V, and at the same angle as the sides of the U. S. F.. thread, the walls of the special thread.V

Generally,.however` to get the required thread depth it will be necessary to have the sides l of theextra bottom portion 6 of grooves between threads at some angle to each other say 30 degrees as shown in Fig. l) less in amount` than the angle between the sides 5 of the thread (60 degrees as shown in Fig. 4) adjacent to the crest.

In the case of coacting members originally made with different uniform pitch of threads, it is immaterial whether the pitch of the threads on the female member be greater or less than the pitch of those on the male member. lt' is, however, preferable to have more threads to the inch in the nut than Von the bolt since this tends to cause the thread helix of the nut to be extended through contact with the bolt, as shown m exaggerated form in F ig. 2. Then, it

through long continueduse the irictional which Vcoaeting members may be made selflocking: (l) when the special thread is formed withthe same number of threads per inch as the standard, but, before being used, has the distance between some oi its threads permanently increased or decreased; (2) when the special thread on one member has agreater uniform pitch than the standard thread on the other member and (3) when the 'special thread on one member has a smaller uniform pitch than the standard thread on the other member.

Measured in a linecorrespending to the basic pitch line of themember having a. standard thread, the thickness of the special thread will be the same in all three ways and will numerically equal the thickness of the standard thread and the spaces between the standard threads.

rThe spaces between the specialV threads when formed, however, will be dii'erent in each of the three ways. ln way (l), the space between threads will initially be equal to the thickness ol' the thread as in the standard practicegin way (2), the space between'thread's willbe'greater than the thiol;- ness of the thread, and in way (3), the space between threads will be less than the thickness oi Vthe thread.

Although the invention has been herein illustrated in conjunction with the United States standard -i'form of threat, it will be understood that itis equally applicable to threads made in accordance with other standards, and that details of the form illustrated may be altered or omitted without departing from the spirit of this invention as delined by the following claims.

I claim: Y

1. A pair oi"- interiitting members having complementary screw-threads7 differing in pitch respectively, and the thread grooves et one ott' said members being deepened to permit the threads to yield. Y

2. A pair of interitting members having complementary screw-threads didering in pitch.respectively, and the thread grooves of one et said Vmembers being deepened throughout substantially the entire length thereoic to permit the respective thread-helix to be expanded or contracted axially and thereby exert locking pressure on the threads ot' the other member.

3. A pair et interiitting members, one having a screw-thread of standard triangular form and dimensions, and the other hav-A ing a similar thread but differing as to pitch and having deepened thread grooves whereby the thread-helix may yield to accommodate the difference in pitch and thereby preduce a locking pressure between the threads.

l. A pair Tot interitting members having complementary screw-threa ds uniformly differing in pitch throughout their entire length respectively, and the thread grooves of one of said members being deepened to permit the threads to yield.

5. A pair et interiitting men'ibers, the male part having a screw thread ot standard triangular iform, dimensions and pitch, and the female. part having a similar thread but ditl'ering through a part of its length as to pitch and having deepened 'thread grooves whereby the threads et the female part that diifer in pitch trom the threads et the male part with which they cor-.ct may yield to aecommodate the difference in pitch and thereby produce a locking pressure Vbetween the threads.

G. A screw thread having in cross section the same outline and area. from its crest to a place near its bottom, as the standard thread Awith which it may ceact; and from said placeY near its bottom, the sides ci the thread run at such angle that the depth el tl e special thread will be greater than the depth o' the standard thread with which it may ceact. Y Y

7. A screw thread having in cross scat-ion the same outline and area, from its crest to a place near its bottom, as thel standard thread with which it may enact; and irom said place near its bottom to the bottom of the thread, the sides of the thread run at an angle between them less than the angle between the'sides adjacent to the crest.

Signed at Chicagothis-() day et Dee.,

IRVING C. WODWARB 

